U.S. patent application number 12/705939 was filed with the patent office on 2010-12-02 for derivatives of native lignin from annual fibre feedstocks.
Invention is credited to Mikhail Yurevich Balakshin, Alex Berlin, Humbert Thomas Dellicolli, Chadrick Adam Nathaniel Jordan Grunert, Vera Maximenko Gutman, Darwin Ortiz, Edward Kendall Pye.
Application Number | 20100305244 12/705939 |
Document ID | / |
Family ID | 43220959 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100305244 |
Kind Code |
A1 |
Balakshin; Mikhail Yurevich ;
et al. |
December 2, 2010 |
DERIVATIVES OF NATIVE LIGNIN FROM ANNUAL FIBRE FEEDSTOCKS
Abstract
The present invention provides derivatives of native lignin
having a certain aliphatic hydroxyl content. Surprisingly, it has
been found that consistent and predictable antioxidant activity may
be provided by selecting for derivatives of native lignin having a
certain aliphatic hydroxyl content.
Inventors: |
Balakshin; Mikhail Yurevich;
(North Vancouver, CA) ; Berlin; Alex; (Burnaby,
CA) ; Dellicolli; Humbert Thomas; (Hanahan, SC)
; Grunert; Chadrick Adam Nathaniel Jordan; (Vancouver,
CA) ; Gutman; Vera Maximenko; (Burnaby, CA) ;
Ortiz; Darwin; (Delta, CA) ; Pye; Edward Kendall;
(Media, PA) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Family ID: |
43220959 |
Appl. No.: |
12/705939 |
Filed: |
February 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61182044 |
May 28, 2009 |
|
|
|
61233345 |
Aug 12, 2009 |
|
|
|
Current U.S.
Class: |
524/76 ; 530/500;
530/507 |
Current CPC
Class: |
C08L 23/02 20130101;
C08J 3/00 20130101; D21C 11/0007 20130101; C07G 1/00 20130101; C08H
6/00 20130101; Y02P 20/582 20151101; C08L 91/06 20130101; C09K
15/06 20130101; C08L 97/005 20130101; C08L 2201/52 20130101; C08L
2207/04 20130101; A61K 36/54 20130101; C08K 5/13 20130101; Y02P
60/877 20151101; C08J 2397/00 20130101; B27N 3/002 20130101; A61K
36/48 20130101; A23K 10/32 20160501; C08L 97/02 20130101; A23L
33/105 20160801; A61K 36/15 20130101; Y02P 60/87 20151101; C08L
57/00 20130101; A61K 36/76 20130101; D21H 11/00 20130101 |
Class at
Publication: |
524/76 ; 530/500;
530/507 |
International
Class: |
C08L 97/00 20060101
C08L097/00; C07G 1/00 20060101 C07G001/00 |
Claims
1. An annual fibre lignin derivative wherein said lignin derivative
has an aliphatic hydroxyl content of from about 1 mmol/g to about
3.75 mmol/g.
2. A lignin derivative according to claim 1 wherein the derivative
has an aliphatic hydroxyl content is from about 1.5 mmol/g to about
3.5 mmol/g.
3. A lignin derivative according to claim 1 wherein the lignin is
derived from biomass comprising flax; cereal straw (wheat, barley,
oats); bagasse; corn; hemp, fruit pulp, alfa grass, or
combinations/hybrids thereof.
4. A lignin derivative according to claim 1 wherein the lignin is
derived from biomass comprising wheat straw, bagasse, corn cobs, or
combinations/hybrids thereof.
5. A lignin derivative according to claim 1 having a normalized RSI
of 15 or greater.
6. A lignin derivative according to claim 1 wherein the derivative
comprises alkoxy groups.
7. A lignin derivative according to claim 1 wherein the derivative
comprises ethoxyl groups.
8. A lignin derivative according to claim 1 wherein the ethoxyl
content is 1.4 mmol/g or less.
9. Use of a lignin derivative according to claim 1 as an
antioxidant.
10. Use of a lignin derivative according to claim 1 as an
antioxidant for thermoplastics.
11. Use of a lignin derivative according to claim 1 in a
nutritional supplement, nutraceutical, animal feed, and/or
functional food.
12. A composition comprising the derivative of claim 1 and a
polymer-forming component.
13. A thermoplastic composition comprising a lignin derivative
according to claim 1.
14. A polyolefin composition comprising a lignin derivative
according to claim 1.
15. A method of producing a lignin derivative according to claim 1,
said method comprising: a) pulping a fibrous biomass in a vessel
with an organic solvent/water solvent solution to form a liquor,
wherein the solution comprises about 30% or greater, by weight, of
organic solvent and the pH of the liquor is from about 1 to about
6; b) heating the liquor to about 100.degree. C. or greater; c)
maintaining the elevated temperature and pressure for 1 minute or
longer; d) separating the cellulosic pulps from the pulping liquor;
and e) recovering derivatives of native lignin.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 61/182,044, filed on May 28, 2009, and U.S.
Provisional Patent Application Ser. No. 61/233,345, filed Aug. 12,
2009, the contents of which are incorporated in their entirety
herein by reference.
FIELD
[0002] This invention relates to derivatives of native lignin
recovered from lignocellulosic feedstocks, and industrial
applications thereof. More particularly, this invention relates to
derivatives of native lignin having certain chemical properties as
well as uses, processes, methods, and compositions thereof.
BACKGROUND
[0003] Native lignin is a naturally occurring amorphous complex
cross-linked organic macromolecule that comprises an integral
component of all plant biomass. The chemical structure of lignin is
irregular in the sense that different structural units (e.g.,
phenylpropane units) are not linked to each other in any systematic
order. It is known that native lignin comprises pluralities of two
monolignol monomers that are methoxylated to various degrees
(trans-coniferyl alcohol and trans-sinapyl alcohol) and a third
non-methoxylated monolignol (trans-p-coumaryl alcohol). Various
combinations of these monolignols comprise three building blocks of
phenylpropanoid structures i.e. guaiacyl monolignol, syringyl
monolignol and p-hydroxyphenyl monolignol, respectively, that are
polymerized via specific linkages to form the native lignin
macromolecule. Extracting native lignin from lignocellulosic
biomass during pulping generally results in lignin fragmentation
into numerous mixtures of irregular components. Furthermore, the
lignin fragments may react with any chemicals employed in the
pulping process. Consequently, the generated lignin fractions can
be referred to as lignin derivatives and/or technical lignins. As
it is difficult to elucidate and characterize such complex mixture
of molecules, lignin derivatives are usually described in terms of
the lignocellulosic plant material used, and the methods by which
they are generated and recovered from lignocellulosic plant
material, i.e. hardwood lignins, softwood lignins, and annual fibre
lignins.
[0004] Native lignins are partially depolymerized during the
pulping processes into lignin fragments which dissolve in the
pulping liquors and subsequently separated from the cellulosic
pulps. Post-pulping liquors containing lignin and polysaccharide
fragments, and other extractives, are commonly referred to as
"black liquors" or "spent liquors", depending on the pulping
process. Such liquors are generally considered a by-product, and it
is common practice to combust them to recover some energy value in
addition to recovering the cooking chemicals. However, it is also
possible to precipitate and/or recover lignin derivatives from
these liquors. Each type of pulping process used to separate
cellulosic pulps from other lignocellulosic components produces
lignin derivatives that are very different in their
physico-chemical, biochemical, and structural properties.
[0005] Given that lignin derivatives are available from renewable
biomass sources there is an interest in using these derivatives in
certain industrial applications. For example, lignin derivatives
obtained via organosolv extraction, such as the Alcell.RTM. process
(Alcell is a registered trademark of Lignol Innovations Ltd.,
Burnaby, BC, CA), have been used in rubber products, adhesives,
resins, plastics, asphalt, cement, casting resins, agricultural
products, oil-field products and as feedstocks for the production
of fine chemicals.
[0006] However, large-scale commercial application of the extracted
lignin derivatives, particularly those isolated in traditional
pulping processes employed in the manufacture of pulp for paper
production, has been limited due to, for example, the inconsistency
of their chemical and functional properties. This inconsistency
may, for example, be due to changes in feedstock supplies and the
particular extraction/generation/recovery conditions. These issues
are further complicated by the complexity of the molecular
structures of lignin derivatives produced by the various extraction
methods and the difficulty in performing reliable routine analyses
of the structural conformity and integrity of recovered lignin
derivatives. For instance, lignin derivatives are known to have
antioxidant properties (e.g. Catignani G. L., Carter M. E.,
Antioxidant Properties of Lignin, Journal of Food Science, Volume
47, Issue 5, 1982, p. 1745; Pan X. et al. J. Agric. Food Chem.,
Vol. 54, No. 16, 2006, pp. 5806-5813) but, to date, these
properties have been highly variable making the industrial
application of lignin derivatives as an antioxidant
problematic.
[0007] Thermoplastics and thermosets are used extensively for a
wide variety of purposes. Examples of thermoplastics include
classes of polyesters, polycarbonates, polylactates, polyvinyls,
polystyrenes, polyamides, polyacetates, polyacrylates,
polypropylene, and the like. Polyolefins such as polyethylene and
polypropylene represent a large market, amounting to more than 100
million metric tons annually. During manufacturing, processing and
use the physical and chemical properties of certain thermoplastics
can be adversely affected by various factors such as exposure to
heat, UV radiation, light, oxygen, mechanical stress or the
presence of impurities. Clearly it is advantageous to mitigate or
avoid these problems. In addition, the increase in recycling of
material has led to an increased need to address these issues.
[0008] Degradation caused by free radicals, exposure to UV
radiation, heat, light, and environmental pollutants are frequent
causes of the adverse effects. A stabilizer such as an antioxidant,
anti-ozonant, or UV block is often included in thermoplastic resins
for the purpose of aiding in the production process and extending
the useful life of the product. Common examples of stabilizers and
antioxidants include amine types, phenolic types, phenol alkanes,
phosphites, and the like. These additives often have undesirable or
even unacceptable environmental, health and safety, economic,
and/or disposal issues associated with their use. Furthermore,
certain of these stabilizers/antioxidants can reduce the
biodegradability of the product.
[0009] It has been suggested that lignin may provide a suitable
polymeric natural antioxidant which has an acceptable good
toxicity, efficacy, and environmental profile. See, for example, A.
Gregorova et al., Radical scavenging capacity of lignin and its
effect on processing stabilization of virgin and recycled
polypropylene, Journal of Applied Polymer Science 106-3 (2007) pp.
1626-1631; C. Pouteau et al. Antioxidant Properties of Lignin in
Polypropylene, Polymer Degradation and Stability 81 (2003) 9-18.
Despite the advantages of lignin, for a variety of reasons, it has
not been adopted for widespread use as an antioxidant. For
instance, it is often problematic to provide lignins that perform
consistently in terms of antioxidant activity. Also, the processing
of the lignin may introduce substances that are incompatible for
use with chemicals such as polyolefins. Additionally, the cost of
producing and/or purifying the lignin may make it uneconomic for
certain uses.
SUMMARY
[0010] The present invention provides derivatives of native lignin
having a certain aliphatic hydroxyl content. Surprisingly, it has
been found that consistent and predictable antioxidant activity may
be provided by selecting for derivatives of native lignin having
certain aliphatic hydroxyl contents.
[0011] As used herein, the term "native lignin" refers to lignin in
its natural state, in plant material.
[0012] As used herein, the terms "lignin derivatives" and
"derivatives of native lignin" refer to lignin material extracted
from lignocellulosic biomass. Usually, such material will be a
mixture of chemical compounds that are generated during the
extraction process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows the quantitative .sup.13C NMR spectrum of
non-acetylated sugarcane bagasse lignin derivatives.
[0014] FIG. 2 shows the quantitative .sup.13C NMR spectrum of
acetylated sugarcane bagasse lignin derivatives.
DETAILED DESCRIPTION
[0015] The present invention provides derivatives of native lignin
from annual feedstocks having certain aliphatic hydroxyl contents.
It has been found that the aliphatic hydroxyl content of lignin
derivatives can be correlated to the Radical Scavenging Index
(RSI), a measure of antioxidant activity. Thus, selecting for
derivatives of native lignin having a certain aliphatic hydroxyl
content results in a product having a more consistent level of
antioxidant activity. It has been found that derivatives of native
lignin from annual feedstocks having an aliphatic hydroxyl content
of about 1 mmol/g to about 3.75 mmol/g have a predictable level of
antioxidant activity.
[0016] Radical Scavenging Index (RSI) is a measure of radical
scavenging capacity. The assay uses 2,2-diphenyl-1-picrylhydrazyl
(DPPH), a stable free radical which absorbs light strongly at 515
nm, to measure a compound's radical scavenging index (RSI). In its
radical form, DPPH.cndot.absorbs strongly at 515 nm and has a deep
purple colour. As DPPH gives up its free electron to radical
scavengers, it loses its purple colour and its absorbance shifts to
520 nm. The greater the drop in DPPH absorbance at 515 nm after a
test compound has been added to the DPPH solution, the higher the
compound's free RSI and also, its antioxidant activity. In the
present invention, Vitamin E (Vit. E) and butylated hydroxytoluene
(BHT) are used as positive controls. The lignin derivative samples
(1.0-2.0 mg), Vit. E control samples (1.0-2.0 mg), and BHT control
samples (6.0-8.0 mg) are prepared for testing by being placed into
microcentrifuge tubes after which each was diluted with 1.0 mL of
90% (v/v) aqueous dioxan, vortexed, transferred to new
microcentrifuge tubes and further diluted 50/50 with 90% aqueous
dioxane to give stock concentrations of 0.5-1.0 mg/mL for samples
and Vitamin E and 3.0-4.0 mg/mL for BHT. An indicating (purple)
DPPH stable free radical solution is made by dissolving 3.78 mg
DPPH in 100 mL 90% dioxane (95.9 .mu.M). Samples and standards are
serially diluted to fill columns of a quartz 96-well plate (8
dilutions). The assays are performed by placing aliquots of the
sample stock solutions into two rows of wells in a 96-well plate.
The first row served as the reference row while the second row
received DPPH aliquots. 165 .mu.L of 90% dioxane was added to each
well and mixed. Aliquots of the mixed samples in each row are
transferred to the adjacent row which is further diluted with 165
.mu.L of 90% dioxane in each well. The mixing, transferring and
dilution are repeated until the last row of wells is prepared. The
same volume of aliquots is removed from the last row. The 96-well
plate also contains a row of wells that received only the 90%
dioxane. In the final step of the preparation procedure, 165 .mu.L
of the DPPH solution is added as quickly as possible to all the
control and analytical columns by using an 8-channel auto-pipette
and an Eppendorf.RTM. reagent reservoir. As soon as all reagents
are added, the plate is placed into a plate-reading
spectrophotometer (Spectra Max Plus, Molecular Devices, Sunnyvale,
Calif., USA), and absorbance measurements are carried out. The
program for the spectrophotometer (SOFTmax software) consists of a
timing sequence of 16 min and a reading of the entire plate at 515
nm. RSI is defined as the inverse of the concentration which
produces 50% inhibition in DPPH absorbance at 515 nm. The results
are then `normalized` by dividing the sample RSI by the RSI value
for the BHT control. The normalized RSI is represented by this
acronym "NRSI".
[0017] In the present invention, "aliphatic hydroxyl content"
refers to the quantity of aliphatic hydroxyl groups in the lignin
derivatives and is the arithmetic sum of the quantity of primary
and secondary hydroxyl groups (OHal=OHpr+OHsec). The aliphatic
hydroxyl content can be measured by quantitative .sup.13C high
resolution NMR spectroscopy of acetylated and non-acetylated lignin
derivatives, using, for instance, 1,3,5-trioxane and tetramethyl
silane (TMS) as internal references. For the data analysis
"BASEOPT" (DIGMOD set to baseopt) routine in the software package
TopSpin 2.1.4 was used to predict the first FID data point back at
the mid-point of .sup.13C r.f. pulse in the digitally filtered data
was used. For the NMR spectra recording a Bruker AVANCE II digital
NMR spectrometer running TopSpin 2.1 was used. The spectrometer
used a Bruker 54 mm bore Ultrashield magnet operating at 14.1 Tesla
(600.13 MHz for .sup.1H, 150.90 MHz for .sup.13C). The spectrometer
was coupled with a Bruker QNP cryoprobe (5 mm NMR samples, .sup.13C
direct observe on inner coil, .sup.1H outer coil) that had both
coils cooled by helium gas to 20K and all preamplifiers cooled to
77K for maximum sensitivity. Sample temperature was maintained at
300 K.+-.0.1 K using a Bruker BVT 3000 temperature unit and a
Bruker BCU05 cooler with ca. 95% nitrogen gas flowing over the
sample tube at a rate of 800 L/h.
[0018] Quantification of ethoxyl groups was performed similarly to
aliphatic hydroxyls quantification by high resolution .sup.13C NMR
spectroscopy. Identification of ethoxyl groups was confirmed by 2D
NMR HSQC spectroscopy. 2D NMR spectra were recorded by a Bruker 700
MHz UltraShield Plus standard bore magnet spectrometer equipped
with a sensitive cryogenically cooled 5 mm TCI gradient probe with
inverse geometry. The acquisition parameters were as follow:
standard Bruker pulse program hsqcetgp, temperature of 298 K, a
90.degree. pulse, 1.1 sec pulse delay (d1), and acquisition time of
60 msec.
[0019] The present invention provides derivatives of native lignin
recovered during or after pulping of lignocellulosic feedstocks.
The pulp may be from any suitable lignocellulosic feedstock such as
from annual fibre feedstocks. Annual fibre feedstocks include
biomass derived from annual plants, plants which complete their
growth in one growing season and therefore must be planted yearly.
Examples of annual fibers include: flax, cereal straw (wheat,
barley, oats), sugarcane bagasse, rice straw, corn stover, corn
cobs, hemp, fruit pulp, alfa grass, switchgrass, and
combinations/hybrids thereof. Industrial residues like corn cobs,
fruit peals, seeds, etc. may also be considered annual fibers since
they are commonly derived from annual fibre biomass such as edible
crops and fruits. For example, the annual fibre feedstock may be
selected from wheat straw, corn stover, corn cobs, sugar cane
bagasse, and combinations/hybrids thereof.
[0020] Derivatives of native lignin according to the present
invention, coming from annual fibre feedstocks tend to have a NRSI
of about 100 or less, about 90 or less, about 80 or less, about 70
or less, about 60 or less.
[0021] In the present invention, derivatives of native lignin from
annual fibre feedstocks may have an aliphatic hydroxyl content of,
for example, about 3.75 mmol/g or less; about 3.5 mmol/g or less;
about 3.25 mmol/g or less; about 3 mmol/g or less; about 2.75
mmol/g or less; about 2.5 mmol/g or less; about 2.35 mmol/g or
less; about 2.25 mmol/g or less.
[0022] In the present invention, derivatives of native lignin from
annual fibre feedstocks may have an aliphatic hydroxyl content of,
for example, about 1 mmol/g or greater; about 1.1 mmol/g or
greater; about 1.2 mmol/g or greater; about 1.3 mmol/g or greater;
about 1.4 mmol/g or greater; about 1.5 mmol/g or greater.
[0023] The derivatives of native lignin will vary with the type of
process used to separate native lignins from cellulose and other
biomass constituents. Preparations very similar to native lignin
can be obtained by (1) solvent extraction of finely ground wood
(milled-wood lignin, MWL) or by (2) acidic dioxane extraction
(acidolysis) of wood. Derivatives of native lignin can be also
isolated from biomass pre-treated using (3) steam explosion, (4)
dilute acid hydrolysis, (5) ammonia fibre expansion, (6)
autohydrolysis methods. Derivatives of native lignin can be
recovered after pulping of lignocellulosics including industrially
operated (3) kraft and (4) soda pulping (and their modifications)
and (5) sulphite pulping. In addition, a number of various pulping
methods have been developed but not industrially introduced. Among
them four major "organosolv" pulping methods tend to produce
highly-purified lignin mixtures. The first organosolv method uses
ethanol/solvent pulping (aka the Alcell.RTM. process); the second
organosolv method uses alkaline sulphite anthraquinone methanol
pulping (aka the "ASAM" process); the third organosolv process uses
methanol pulping followed by methanol, NaOH, and anthraquinone
pulping (aka the "Organocell" process); the fourth organosolv
process uses acetic acid/hydrochloric acid or formic acid pulping
(aka the "Acetosolv" process).
[0024] It should be noted that kraft pulping, sulphite pulping, and
ASAM organosolv pulping will generate derivatives of native lignin
containing significant amounts of organically-bound sulphur which
may make them unsuitable for certain uses. Acid hydrolysis, soda
pulping, steam explosion, Alcell.RTM. pulping, Organocell pulping,
and Acetosolv pulping will generate derivatives of native lignin
that are sulphur-free or contain low amounts of inorganic
sulphur.
[0025] Organosolv processes, particularly the Alcell.RTM. process,
tend to be less aggressive and can be used to separate highly
purified lignin derivatives and other useful materials from biomass
without excessively altering or damaging the native lignin building
blocks. Such processes can therefore be used to maximize the value
from all the components making up the biomass. Organosolv
extraction processes however typically involve extraction at higher
temperatures and pressures with a flammable solvent compared to
other industrial processes and thus are generally considered to be
more complex and expensive.
[0026] A description of the Alcell.RTM. process can be found in
U.S. Pat. No. 4,764,596 (herein incorporated by reference). The
process generally comprises pulping or pre-treating a fibrous
biomass feedstock with primarily an ethanol/water solvent solution
under conditions that include: (a) 60% ethanol/40% water (w/w), (b)
temperature of about 180.degree. C. to about 210.degree. C., (c)
pressure of about 20 atm to about 35 atm, and (d) a processing time
of 5 to 120 minutes. Native lignins are degraded during pulping and
their derivatives are dissolved into the pulping liquor which also
receives solubilised hemicelluloses, other saccharides,
carbohydrate-degradation products such as furfural, 5-hydroxymethyl
furfural, acetic, levulinic, formic, and other organic acids
derived from carbohydrates and extractives such as lipophilic
extractives, phenols, and tannins. Organosolv pulping liquors are
often called "black liquors". The organic acids released by
organosolv pulping significantly acidify the black liquors to pH
levels of about 5 and lower. After separation from the cellulosic
pulps produced during the pulping process, the derivatives of
native lignin are recovered from the black liquors by
depressurization followed by flashing with cold water which will
cause the fractionated derivatives of native lignin to precipitate
thereby enabling their recovery by standard solids/liquids
separation processes. Various disclosures exemplified by U.S. Pat.
No. 7,465,791 and PCT Patent Application Publication No. WO
2007/129921, describe modifications to the Alcell organosolv
process for the purposes of increasing the yields of fractionated
derivatives of native lignin recovered from fibrous biomass
feedstocks during biorefining. Modifications to the Alcell
organosolv process conditions included adjusting: (a) ethanol
concentration in the pulping liquor to a value selected from a
range of 35%-85% (w/w) ethanol, (b) temperature to a value selected
from a range of 100.degree. C. to 350.degree. C., (c) pressure to a
value selected from a range of 5 atm to 35 atm, and (d) processing
time to a duration from a range of 20 minutes to about 2 hours or
longer, (e) liquor-to-wood ratio of 3:1 to 15:1 or higher, (f) pH
of the cooking liquor from a range of 1 to 6.5 or higher if a basic
catalyst is used.
[0027] The present invention provides a process for producing
derivatives of native lignin, said process comprising:
[0028] (a) pulping a fibrous biomass feedstock with an organic
solvent/water solution,
[0029] (b) separating the cellulosic pulps or pre-treated
substrates from the pulping liquor or pre-treatment solution,
[0030] (c) recovering derivatives of native lignin.
[0031] The organic solvent may be selected from short chain primary
and secondary alcohols, such as methanol, ethanol, propanol, and
combinations thereof. For example, the solvent may be ethanol. The
liquor solution may comprise about 20%, by weight, or greater,
about 30% or greater, about 50% or greater, about 60% or greater,
about 70% or greater, of ethanol.
[0032] Step (a) of the process may be carried out at a temperature
of from about 100.degree. C. and greater, or about 120.degree. C.
and greater, or about 140.degree. C. and greater, or about
160.degree. C. and greater, or about 170.degree. C. and greater, or
about 180.degree. C. and greater. The process may be carried out at
a temperature of from about 300.degree. C. and less, or about
280.degree. C. and less, or about 260.degree. C. and less, or about
240.degree. C. and less, or about 220.degree. C. and less, or about
210.degree. C. and less, or about 205.degree. C. and less, or about
200.degree. C. and less.
[0033] Step (a) of the process may be carried out at a pressure of
about 5 atm and greater, or about 10 atm and greater, or about 15
atm and greater, or about 20 atm and greater, or about 25 atm and
greater, or about 30 atm and greater. The process may be carried
out at a pressure of about 150 atm and less, or about 125 atm and
less, or about 115 atm and less, or about 100 atm and less, or
about 90 atm and less, or about 80 atm and less.
[0034] The fibrous biomass may be treated with the solvent solution
of step (a) for about 1 minute or more, about 5 minutes or more,
about 10 minutes or more, about 15 minutes or more, about 30
minutes or more. The fibrous biomass may be treated with the
solvent solution of step (a) at its operating temperature for about
360 minutes or less, about 300 minutes or less, about 240 minutes
or less, about 180 minutes or less, about 120 minutes or less.
[0035] The pH of the pulp liquor may, for example, be from about 1
to about 6, or from about 1.5 to about 5.5.
[0036] The weight ratio of liquor to biomass may be any suitable
ratio. For example, from about 5:1 to about 15:1, from about 5.5:1
to about 10:1; from about 6:1 to about 8:1.
[0037] The present invention provides a process for producing a
lignin derivative from an annual fibre feedstock having an
aliphatic hydroxyl content of from about 1 mmol/g to about 3.75
mmol/g. Said process comprises: [0038] a) pulping or pre-treating a
fibrous biomass feedstock in a vessel with an organic solvent/water
solvent solution to form a liquor, wherein: [0039] i. the solution
comprises about 30% or greater, by weight, of organic solvent; and
[0040] ii. the pH of the liquor is from about 1 to about 5.5;
[0041] b) heating the liquor to about 100.degree. C. or greater;
[0042] c) raising the pressure in the vessel to about 5 atm or
greater; [0043] d) maintaining the elevated temperature and
pressure for 1 minute or longer; [0044] e) separating the
cellulosic pulps from the pulp liquor [0045] f) recovering
derivatives of native lignin.
[0046] The derivatives of native lignin herein may be incorporated
into polymer compositions. The compositions herein may comprise a
lignin derivative according to the present invention and a
polymer-forming component. As used herein, the term
`polymer-forming component` means a component that is capable of
being polymerized into a polymer as well as a polymer that has
already been formed. For example, in certain embodiments the
polymer-forming component may comprise monomer units which are
capable of being polymerized. In certain embodiments the polymer
component may comprise oligomer units that are capable of being
polymerized. In certain embodiments the polymer component may
comprise a polymer that is already substantially polymerized.
[0047] Polymers forming components for use herein may result in
thermoplastic or thermoset polymers such as epoxy resins,
urea-formaldehyde resins, phenol-formaldehyde resins, polyimides,
and the like. For example, polyalkenes such as polyethylene or
polypropylene.
[0048] Typically, the lignin derivative will comprise from about
0.1%, by weight, or greater, about 0.5% or greater, about 1% or
greater, of the composition. Typically, the lignin derivative will
comprise from about 80%, by weight, or less, about 60% or less,
about 40% or less, about 20% or less, about 10% or less, of the
composition.
[0049] The compositions comprise lignin derivative and
polymer-forming component but may comprise a variety of other
optional ingredients such as adhesion promoters; biocides
(antibacterials, fungicides, and moldicides), anti-fogging agents;
anti-static agents; bonding, blowing and foaming agents;
dispersants; fillers and extenders; fire and flame retardants and
smoke suppressants; impact modifiers; initiators; lubricants;
micas; pigments, colorants and dyes; plasticizers; processing aids;
release agents; silanes, titanates and zirconates; slip and
anti-blocking agents; stabilizers; stearates; ultraviolet light
absorbers; foaming agents; defoamers; hardeners; odorants;
deodorants; antifouling agents; viscosity regulators; waxes; and
combinations thereof.
[0050] The present invention provides the use of the present
derivatives of native lignin as an antioxidant. For example, the
present use may be as an antioxidant additive for use with
thermoplastic polymers such as polyethylene, polypropylene,
polyamides, styrene-butadiene, natural rubber, and combinations
thereof.
[0051] The present invention provides methods of producing annual
fibre derivatives of native lignin having an aliphatic hydroxyl
content of about 3.75 mmol/g or less; 3.5 mmol/g or less; 3.25
mmol/g or less; 3 mmol/g or less; 2.75 mmol/g or less; 2.5 mmol/g
or less; 2.35 mmol/g or less; 2.25 mmol/g or less. The present
invention provides methods of producing annual fibre derivatives of
native lignin having an aliphatic hydroxyl content of about 1
mmol/g or greater; about 1.1 mmol/g or greater; about 1.2 mmol/g or
greater; about 1.3 mmol/g or greater; about 1.4 mmol/g or greater;
about 1.5 mmol/g or greater.
[0052] The present invention provides methods of producing annual
fibre derivatives of native lignin having a normalized RSI of 15 or
greater, 20 or greater, 25 or greater, 30 or greater, 35 or
greater. The present invention provides methods of producing annual
fibre derivatives of native lignin having a normalized RSI of about
100 or less, about 90 or less, about 80 or less, about 70 or less,
about 60 or less.
[0053] The present invention provides lignin derivatives comprising
alkoxy groups. For example, the present lignin derivatives may have
an alkoxy content of 2 mmol/g or less; about 1.4 mmol/g or less;
about 1.2 mmol/g or less; about 1 mmol/g or less; about 0.8 mmol/g
or less; about 0.7 mmol/g or less; about 0.6 mmol/g or less; about
0.5 mmol/g or less; about 0.4 mmol/g or less; about 0.3 mmol/g or
less. The present lignin derivatives may have an alkoxy content of
0.001 mmol/g or greater, about 0.01 mmol/g of greater, about 0.05
mmol/g or greater, about 0.1 mmol/g or greater.
[0054] The present invention provides lignin derivatives comprising
ethoxyl groups. For example, the present lignin derivatives may
have an ethoxyl content of 2 mmol/g or less; about 1.4 mmol/g or
less; about 1.2 mmol/g or less; about 1 mmol/g or less; about 0.8
mmol/g or less; about 0.7 mmol/g or less; about 0.6 mmol/g or less;
about 0.5 mmol/g or less; about 0.4 mmol/g or less; about 0.3
mmol/g or less. The present lignin derivatives may have an ethoxyl
content of 0.001 mmol/g or greater, about 0.01 mmol/g of greater,
about 0.05 mmol/g or greater, about 0.1 mmol/g or greater.
[0055] The present lignin derivatives may have any suitable
phenolic hydroxyl content such as from about 2 mmol/g to about 8
mmol/g. For example, the phenolic hydroxyl content may be from
about 2.5 mmol/g to about 7 mmol/g; about 3 mmol/g to about 6
mmol/g.
[0056] The present lignin derivatives may have any suitable number
average molecular weight (Mn). For example, the Mn may be from
about 200 g/mol to about 3000 g/mol; about 350 g/mol to about 2000
g/mol; about 500 g/mol to about 1500 g/mol.
[0057] The present lignin derivatives may have any suitable weight
average molecular weight (Mw). For example, the Mw may be from
about 500 g/mol to about 5000 g/mol; about 750 g/mol to about 4000
g/mol; about 900 g/mol to about 3500 g/mol.
[0058] The present lignin derivatives may have any suitable
polydispersity (D). For example, the D may be from about 1 to about
5; from about 1.2 to about 4; from about 1.3 to about 3.5; from
about 1.4 to about 3.
[0059] The present lignin derivatives are preferably hydrophobic.
Hydrophobicity may be assessed using contact angle
measurements.
[0060] It has been suggested that lignins or lignin derivatives may
be used in nutritional supplements (e.g. Baurhoo et. al., Purified
Lignin: Nutritional and Health Impacts on Farm Animals--A Review,
Animal Feed Science and Technology 144 (2008) 175-184). The present
derivatives of native lignin may be used in nutritional
supplements, nutraceuticals, functional foods, and the like. The
stable and consistent antioxidant activity may be advantageous when
formulating such compositions.
[0061] The present derivatives of native lignin may be used for
other purposes such as, for example, laminates, stains, pigments,
inks, adhesives, coatings, rubbers, elastomers, plastics, films,
paints, carbon fibre composites, panel boards, print-circuit
boards, lubricants, surfactants, oils, animal feed, food and
beverages, and the like.
EXAMPLES
Example 1
Recovery of Lignin Derivatives from Annual Fibre Feedstocks
[0062] Annual fibre feedstock pretreated biomass was prepared from:
(1) wheat straw produced in Alberta, Canada, (2) bagasse produced
from sugarcane grown and processed in Brazil, and (3) corn cobs
produced in Europe. Five samples of wheat straw biomass were
individually pulped using an acid-catalysed ethanol organosolv
pulping process wherein a different set of pulping conditions was
used for each sample (Table 1). Process conditions for pulping five
samples of sugarcane bagasse biomass are shown in Table 2. Process
conditions for pulping five samples of shredded corn cob biomass
are shown in Table 3.
TABLE-US-00001 TABLE 1 Pulping conditions for wheat straw biomass
samples at 6:1 liquor-to-wood ratio. Time Temperature Run pH Acid %
min .degree. C. Ethanol % PL % 1 2.86 0.30 90 195 41 38.17 2 2.26
0.90 49 192 37 37.01 3 2.24 2.00 48 184 65 43.48 4 2.03 2.00 77 176
42 40.81 5 2.45 1.00 79 178 49 39.27
TABLE-US-00002 TABLE 2 Pulping conditions for sugarcane bagasse
biomass samples at 6:1 liquor-to-wood ratio. Time Temperature Run
pH Acid % min .degree. C. Ethanol % PL % 1 2.19 2.50 61 178 66
49.76 2 2.01 3.00 23 170 66 39.56 3 2.19 2.00 54 164 58 44.95 4
2.93 0.40 69 184 42 30.26 5 3.26 0.30 32 197 51 42.14
TABLE-US-00003 TABLE 3 Pulping conditions for corn cob biomass
samples at 6:1 liquor-to-wood ratio. Time Temperature Run pH Acid %
min .degree. C. Ethanol % PL % 1 2.18 2.20 100 190 67 56.58 2 2.21
2.00 48 184 65 49.62 3 2.11 1.50 106 176 38 32.28 4 2.31 1.30 94
178 61 47.72 5 2.50 0.70 59 182 45 37.77
[0063] For each biomass sample, the ethanol pulping solvent was
prepared to the specified concentration by first, partially
diluting the ethanol with water after which, a suitable amount of
sulphuric acid was added to achieve the target final acidity.
Finally, the ethanol solution was further diluted with water to
achieve the target ethanol concentration.
[0064] The original lignin content of each fibrous biomass
subsample was determined using the methods described in the
National Renewable Energy Laboratory (NREL) Technical Report
entitled "Determination of Structural Carbohydrates and Lignin in
Biomass"--Laboratory Analytical Procedure (TP-510-42618 (25 Apr.
2008)). Then, after adding the fibrous biomass sample to a pressure
vessel (2 L or 7 L Parr reactor (Parr Instrument Company, Moline,
Ill., USA)) (100-700 g odw chips), the pH-adjusted ethanol-based
pulping solvent was added to the vessel at a 6:1 liquor:wood ratio
& the pH recorded. The vessel was then pressurized and brought
up to the target temperature listed in Tables 1-3 (wheat straw,
bagasse, corn cobs, respectively). The biomass sample was then
"cooked" for the specified period of time, after which, the pulping
process was stopped. After pulping, the contents of pressure vessel
were transferred to a hydraulic 20 ton manual shop press (Airco,
China). The liquor was separated from the solids by first squeezing
the pulped materials in the press to express the liquor. The
expressed liquor was then filtered through a coarse silk screen to
separate expressed chip residues from liquor stream. Next, fine
particles were separated out from the liquor stream by filtration
through fine filter paper (Whatman No 1). The recovered fine
particles represent lignin derivatives that were extracted and
self-precipitated out from the liquor during cooling of the pulped
biomass. The particulate lignin is herein referred to as
self-precipitated lignin derivatives (i.e., "SPL"). The solubilized
lignin derivatives still remaining in the filtered liquor were
precipitated from by dilution with cold water. The lignin
derivatives precipitated by dilution with cold water are referred
to as precipitated lignin or "PL". After determination of the dry
weights of SPL and PL lignin derivatives, the relative yield of
each lignin derivative was determined in reference to total lignin
(sum of the Klason lignin (acid-insoluble lignin) and acid-soluble
lignin) value determined for the original biomass sample before
pulping. The yield of PL lignin derivatives for each sample is
shown in Tables 1-3 on a weight % basis relative to their original
lignin (Klason plus acid-soluble lignin values).
Example 2
Characterization of the Aliphatic Hydroxyl Content of Lignin
Derivatives Recovered from Three Annual Fibre Species
[0065] Functionalized lignin derivatives recovered from annual
fibre biomass samples as described above, were analyzed to
determine the content of primary hydroxyl groups mmol/g sample
(OH-pr mmol/g) and content of secondary hydroxyl groups mmol/g
sample (OH-sec mmol/g). These values were then used to calculate
mmol aliphatic hydroxyl groups/g sample (OH-al mmol/g).
[0066] The hydroxyl contents were determined by quantitative
.sup.13C NMR spectroscopy on a Bruker 600 MHz spectrometer equipped
with Cryoprobe at 300 K using ca 30% solutions of sample in
DMSO-d.sub.6. Chemical shifts were referenced to TMS (0.0 ppm). To
ensure more accurate baseline, especially in the carbonyl region
(215-185 ppm), the spectra were recorded in the interval 240-(-40)
ppm. The following conditions were provided for the quantitative
.sup.13C-NMR: [0067] 1. Inverse gate detection; [0068] 2. a
90.degree. pulse; [0069] 3. Complete relaxation of all nuclei was
achieved by addition of chromium (III) acetylacetonate (0.01 M) and
using a 1.2 s acquisition time and 1.7 s relaxation delay
acquisition parameters.
[0070] The NMR spectra were Fourier-transformed, phased, calibrated
using TMS signals as a reference (0 ppm), and the baseline was
corrected by using a polynomial function. The correction of
baseline was done using the following interval references to be
adjusted to zero: (220-215 ppm)-(185-182 ppm)-(97-92
ppm)-(5-(-20)ppm). No other regions were forced to 0. The signals
in the quantitative .sup.13C NMR spectra were assigned on the basis
of 2D HSQC spectra and a known database. The spectra were
integrated then using the area of internal standard (1S), trioxane,
as the reference. Each spectrum was processed (as described) at
least twice to ensure good reproducibility of the quantification.
Some carboxyl and ester groups resonate in the resonance area of
hydroxyl groups (171.5-166.5 ppm) in the spectra of acetylated
lignins. The amounts of carboxyl and ester groups resonated in the
interval of 171.5-166.5 ppm were determined from the spectra of
non-acetylated lignins. The corrected content of hydroxyl groups
was obtained then by deduction of the amounts of the carboxyl and
ester groups from the corresponding resonances of hydroxyl groups
(Table 4).The calculation of the quantity of the specific moieties
was done as follows:
For non-acetylated lignins: X (mmol/g
lignin)=I.sub.X*m.sub.IS/(30m.sub.Lig*I.sub.IS)*1000
For acetylated lignins: X (mmol/g
lignin)=I.sub.X*m.sub.IS/(30m.sub.Lig*I.sub.IS-42*I.sub.OHtotal*m.sub.IS)-
*1000
[0071] Where X was the amount of the specific moiety; I.sub.X,
I.sub.IS and I.sub.OHtotal were the resonance values of the
specific moiety (Table 4), the internal standard and total OH
groups, correspondingly; m.sub.Lig and m.sub.IS are the masses of
the lignin and internal standard.
[0072] The recorded NMR spectroscopic data are processed and
graphically illustrated as shown in FIGS. 1 and 2. FIG. 1 shows
quantitative .sup.13C NMR spectrum of non-acetylated sugarcane
bagasse lignin derivatives. FIG. 2 shows quantitative .sup.13C NMR
spectrum of acetylated sugarcane bagasse lignin derivatives
TABLE-US-00004 TABLE 4 Symbol I.sub.x in Calculation Equation
Analytical Method OH-pr Resonance at 171.5-169.7 ppm in the
Quantitative .sup.13C High Resolution NMR of mmol/g quantitative
.sup.13C NMR spectra of lignin using 1,3,5-trioxane as internal
acetylated lignins minus resonance at reference 171.5-169.7 ppm in
the quantitative .sup.13C NMR spectra of non-acetylated lignins
OH-sec Resonance at 169.7-169.2 ppm in the Quantitative .sup.13C
High Resolution NMR of mmol/g quantitative .sup.13C NMR spectra of
lignin using 1,3,5-trioxane as internal acetylated lignins minus
resonance at reference 169.7-169.2 ppm in the quantitative .sup.13C
NMR spectra of non-acetylated lignins OH- Resonance at 171.5-165.0
ppm in the Quantitative .sup.13C High Resolution NMR of total
quantitative .sup.13C NMR spectra of lignin using 1,3,5-trioxane as
internal mmol/g acetylated lignins minus resonance at reference
171.5-166.5 ppm in the quantitative .sup.13C NMR spectra of
non-acetylated lignins OH-al OH-al = OH-pr + OH-sec mmol/g OEt
Resonance at 16.0-14.5 ppm in the Quantitative .sup.13C High
Resolution NMR of mmol/g quantitative .sup.13C NMR spectra (both
lignin using 1,3,5-trioxene as internal in acetylated and
non-acetylated reference combined with 2D .sup.1H-.sup.13C NMR
lignins, calculated as average)
[0073] The aliphatic hydroxyl contents of the PL lignin derivatives
from each of the five samples of wheat straw biomass are shown in
Table 5. The contents ranged from 2.03 mmol/g in sample 1.00 to
3.36 mmol/g in sample 5.
TABLE-US-00005 TABLE 5 Aliphatic hydroxyl content and radical
scavenging index of PL lignins recovered from wheat straw biomass.
OH-pr OH-sec OH-al Run mmol/g mmol/g mmol/g NRSI 1 1.20 0.82 2.03
54.03 2 1.36 1.10 2.47 55.32 3 1.67 1.15 2.82 36.63 4 1.66 1.42
3.08 42.18 5 1.80 1.56 3.36 36.82
[0074] The aliphatic hydroxyl contents of the PL lignin derivatives
from each of the five samples of sugarcane bagasse biomass are
shown in Table 6. The contents ranged from 1.74 mmol/g in sample 1
to 2.92 mmol/g in sample 5.
TABLE-US-00006 TABLE 6 Aliphatic hydroxyl content and radical
scavenging index of PL lignins recovered from sugarcane bagasse
biomass. OH-pr OH-sec OH-al Run mmol/g mmol/g mmol/g NRSI 1 1.02
0.73 1.74 52.34 2 1.19 0.89 2.09 41.80 3 1.31 1.02 2.34 38.74 4
1.47 1.05 2.51 37.80 5 1.53 1.39 2.92 39.05
[0075] The aliphatic hydroxyl contents of the PL lignin derivatives
from each of the four samples of corn cob biomass are shown in
Table 7. The contents ranged from 1.58 mmol/g in sample 1 to 3.16
mmol/g in sample 5.
TABLE-US-00007 TABLE 7 Aliphatic hydroxyl content and radical
scavenging index of PL lignins recovered from corn cob biomass.
OH-pr OH-sec OH-al Run mmol/g mmol/g mmol/g NRSI 1 0.95 0.63 1.58
45.15 2 0.50 1.62 2.12 40.34 3 0.82 1.58 2.39 42.20 4 0.80 1.97
2.77 38.30 5 1.37 1.79 3.16 51.41
Example 3
Characterization of the NRSI of Lignin Derivatives Recovered from
Three Annual Fibre Species
[0076] The lignin derivatives samples produced above were assessed
for their radical scavenging index (RSI). The potential antioxidant
activity of each PL lignin derivative was determined by measuring
its radical savaging capacity. The assay used
2,2-diphenyl-1-picrylhydrazyl (DPPH), a stabile free radical which
absorbs light strongly at 515 nm to measure a compound's radical
scavenging index (RSI). In its radical form, DPPH.cndot. absorbs
strongly at 515 nm and has a deep purple colour. As DPPH gives up
its free electron to radical scavengers, it loses its purple colour
and its absorbance shifts to 520 nm. The greater the drop in DPPH
absorbance at 515 nm after a test compound has been added to the
DPPH solution, the higher the compound's free RSI and also, its
antioxidant activity. In the present study, Vit. E and BHT were
used as positive controls. HPLY lignin derivative subsamples
(1.0-2.0 mg), Vit. E control samples (1.0-2.0 mg), and BHT control
samples (6.0-8.0 mg) were prepared for testing by being placed into
epitubes after which, each was diluted with 1.0 mL of 90% (v/v)
aqueous dioxan, vortexed, transferred to new epitubes and then
further diluted 50/50 with 90% aqueous dioxane to give stock
concentrations of 0.5-1.0 mg/mL for samples and Vitamin E and
3.0-4.0 mg/mL for BHT. An indicating (purple) DPPH stable free
radical solution is made by dissolving 3.78 mg DPPH in 100 mL 90%
dioxane (95.9 .mu.M). Samples and standards are serial diluted to
fill columns of a quartz 96-well plate (8 dilutions). The assays
were performed by placing aliquots of the sample stock solutions
into two rows of wells in a 96-well plate. The first row served as
the reference row while the second row received DPPH aliquots. 165
.mu.L of 90% dioxane was added to each well and mixed. Aliquots of
the mixed samples in each row were transferred to the adjacent row
and further diluted with 165 .mu.L of 90% dioxane in each well. The
mixing, transferring and dilution were repeated until the last row
of wells is prepared. The same volume of aliquots was removed from
the last row. The 96-well plate also contained a row of wells that
received only the 90% dioxane. In the final step of the preparation
procedure, 165 .mu.L of the DPPH solution was added to all the
control and analytical columns by using an 8-channel auto-pipette
and an Eppendorf.RTM. reagent reservoir as quickly as possible. As
soon as all reagents are added, the plate is placed into a
plate-reading spectrophotometer (Molecular Devices, Sunnyvale,
Calif., USA, Spectra Max Plus), and absorbance measurements are
commenced. The program for the spectrophotometer (SOFTmax software)
consisted of a timing sequence of 16 min and a reading of the
entire plate at 515 nm. RSI (radical scavenging index) is defined
as the inverse of the concentration which that produced 50%
inhibition in DPPH absorbance at 515 nm. The results were then
`normalized` (NRSI) by dividing the sample RSI by the RSI value for
the BHT control.
[0077] The NRSI values for lignin derivatives recovered from wheat
straw biomass are shown in Table 5. The NRSI values for lignin
derivatives recovered from sugarcane bagasse biomass are shown in
Table 6. The NRSI values for lignin derivatives recovered from corn
cob biomass are shown in Table 7.
* * * * *